Vanilla-Facebook-Theme is a project mainly written in PHP, it's free.
This is a vanilla forum template
How to create a theme:
Copy and paste the "Vanilla-Facebook-Theme" to your vanilla installation, rename the folder to "tweetmylove" or modify the "about.php" file with the right folder name.
Other things you should know:
All non-forum pages should be edited in the global "style.css" file.
If you want to edit the look & feel of the administrative screens, also copy /applications/dashboard/design/admin.css in step 3. Similarly, you can copy other CSS files like /applications/vanilla/design/vanillaprofile.css to customize those pages as well.
If you want to customize the HTML, you can edit that too. Our pages are made up of two parts:
Master Views - these represent everything that wraps the main content of the page. If all you want to do is add a menu or banner above Vanilla, this is all you need to alter. To do so, copy the default master view from /applications/dashboard/views/default.master.php to /themes/yourtheme/views/default.master.php and edit it there.
Views - these represent all of the content in each page. Every application has a "views" folder that contains all of the HTML for every page. So, for example, if you wanted to edit the HTML for the Discussions list, you could copy the views from /applications/vanilla/views/discussions to /themes/yourtheme/views/discussions and edit them there.
You can avoid naming conflicts between applications' views and specify which app a view is for by optionally adding a subfolder with the app's name in /themes/yourtheme/views/ (e.g.: /themes/yourtheme/views/appname/) and placing views there rather than directly in the "views" folder.